1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a cold cathode fluorescent lamp capable of preventing a brightness variation generated when plural cathode fluorescent lamps are simultaneously driven by one driving apparatus, and capable of improving an assembling work and a shock resistance, a container for receiving the same and a liquid crystal display device having the container.
2. Description of the Related Art
As semiconductor technologies and electronic technologies are rapidly developed, data processing technologies are correspondingly rapidly developed to allow processing of a great amount of data in a short time.
Such data processing units output resulted data by processing great amount of data, but do not directly display the resulted data to a user. For this reason, data processed in the data processing unit are displayed through a display device, which acts as an interface between the data processing unit and the user. In this case, data are displayed in the form of letters, images and moving pictures.
The display device performing the above function includes an analog display device and a digital display device. A cathode ray tube (CRT) display device is such an analog display device, while a liquid crystal display (LCD) device is such a digital display device.
The CRT type display device performs the display function by precisely controlling the moving direction of electrons, which are discharged from an electronic gun at a high speed, in a Braun tube. Though the CRT type display device can display an image of high quality, the volume and weight thereof are greatly increased as an effective display area is enlarged. Accordingly, the CRT type display device is often called a “analog type display device”.
To the contrary, the LCD contains a liquid crystal layer having a thickness of a micrometer (μm) unit between two transparent substrates. An electric field is applied, per a minute area unit, to the liquid crystal layer from an inner portion of one of transparent substrates, so that a transmittance degree of light is precisely controlled at each part of the liquid crystal layer.
To realize this, a thin film transistor of a matrix type forms is formed at an inner surface of one of the two opposite substrates. A transparent pixel electrode is formed at an output electrode of the thin film transistor. The pixel electrode is one of two electrodes for applying the electric field to the liquid crystal.
The second electrode for applying the electric field to the liquid crystal is a transparent common electrode formed at an inner surface of the other of the two opposite substrates. A constant reference voltage is supplied to the common electrode.
Hereinafter, a method for controlling the light transmittance degree of the liquid crystal will be described.
Firstly, each thin film transistor is respectively controlled so as to supply a required power into each pixel electrode. At this time, the constant reference voltage is supplied to the common electrode. Accordingly, different electric fields are formed between the pixel electrode and the common electrode, and the alignment of the liquid crystal is precisely varied according to the electric fields. The quantity of light passing through the liquid crystal is also varied according to the variation of the alignment of the liquid crystal. That is, the quantity of the light passing through the liquid crystal is controlled. Then, the light passes through a color pixel (or color filter) formed at a rear side of the common electrode. Accordingly, a full-color display is achieved.
The above-mentioned CRT type display device can display information in any place even where the light does not exist. However, the liquid crystal display device cannot display information in the place where the light is insufficient or does not exist.
This means that the liquid crystal display device is dependent upon the light. For this reason, the light is necessarily required in order to display information in the liquid crystal display device. The light may be an external light, such as sunlight and an illumination light, or the light may be an artificial light created by consuming an electric energy charged in the liquid crystal display device.
When the external light is used, power consumption will be reduced, but information cannot be displayed in the place where the external light does not exist. For this reason, recently, the display of information is carried out using an artificial light, which is created by consuming an electric energy charged in the liquid crystal display device.
A cold cathode fluorescent lamp is mainly used for creating the artificial light, although various kinds of lamps can be used as a device for creating the artificial light. The cold cathode fluorescent lamp has a low heating value, accordingly it prevents the liquid crystal from being liquefied. Also, the cold cathode fluorescent lamp has low power consumption and a long life span.
However, as the effective display area of the liquid crystal display device is enlarged, it is difficult to achieve the required brightness by using only one cold cathode fluorescent lamp. Accordingly, at least two cold cathode fluorescent lamps are adopted in, for example, a middle or large sized notebook computer, monitor and HDTV.
However, if a plurality of cold cathode fluorescent lamps is used, there are various problems not expected when using only one cold cathode fluorescent lamp.
Particularly, the problems frequently arise when a plurality of cold cathode fluorescent lamps are connected in parallel to one power supply device.
When a plurality of cold cathode fluorescent lamps is connected in parallel to one power supply device, a cold cathode fluorescent lamp having a relatively better current-flow characteristic is gradually brightened, and a cold cathode fluorescent lamp having a relatively worse current-flow characteristic is gradually darkened.
Accordingly, it is required to develop a technique for solving the nonuniform brightness problem generated when plural cold cathode fluorescent lamps are connected in parallel to one power supply device.